Verb (5-dan, ぶ, intransitive)
1. to grow wild; to run to waste; to become degenerate
2. to become rough (of art, craft, etc.); to lose refinement; to deteriorate (of skill)
Auxiliary verb (5-dan, ぶ, intransitive)
3. to intensify (of wind, rain, etc.); to become more severe
usu. after -masu stem
Archaic
Verb (5-dan, ぶ, intransitive)
4. to do as one pleases; to amuse oneself; to play around